Activity Dependent Neurotrophic Factor (ADNF), a survival-promoting protein released from glial cells by vasoactive intestinal peptide (VIP), was found to be a 16 kDalton, monomeric protein with a pI of 8.2. ADNF has a unique amino acid sequence. The neurotrophic action of ADNF (EC50 < 1 fM) was isolated to a 15 amino acid peptide (ADNF-15). This peptide was synthesized and was found to be fully active in neuronal survival assays. Neutralizing antiserum was obtained to both intact ADNF (mouse polyclonal) and to ADNF-15 (rabbit polyclonal). Each antisera produced neuronal cell death in CNS cultures. Administration of a VIP antagonist to pregnant mice (E9-E11) produced a severe microcephaly characterized by a 50% reduction in brain weight and DNA content. In animals with VIP antagonist-induced microcephaly, delays in developmental milestones were observed in 10 of 10 behavioral tests. Serum VIP levels in pregnant rats at mid-gestation showed a 6 to 10-fold increase in concentration, while alpha MSH and somatostatin remained unchanged. A novel VIP agonist was synthesized and shown to be 100-fold more potent than VIP in producing neuroprotective actions in CNS cultures. This compound was shown to preferentially interact with VIP receptors in the CNS that mediate neuronal survival. VIP was shown to increase the release of eight cytokines in astrocyte cultures: M-CSF, G-CSF, IL-1 alpha and beta, IL-3, IL-6, TNF-alpha and interferon gamma. IL-1 alpha was found to have an age-dependent affect on neuronal survival in spinal cord cultures.